Means for protecting contents of oil-containing tanks against ignition by electrical discharge.



W. DODD. MEANS FOR PRoTEcTTNG CONTENTS 0F olL coNTAiNTNG TANKS AGAINSTIGNITION BY ELECTRICAL DISCHARGE.

APPLICATION FILED NOV. 5, 1913.

Patented Got. 5, 1915.

$00000 0000,10 ./rQM00N00000000 00000 .09 M0 l 00 q Y OO UNITED sTATEsPATENT oEEicE.

WEST DODD, OF DES MOINES, IOWA.

vMEANS FOR PROTEGTING `COl\T.'fI]-l`1fTS OF OIIi-CONTAINING TANKSAGAINST IGNITION y BY ELECTRICAL DISCHARGE.

Specification of Letters Patent.

Patented 0011.5, 1915.

Application filed November 5, 1913. Serial No. 799,279.

To all whom t may concern.'

' Be it known that I, VVEsT DoDD, a citizen of the United States,residing at Des Moines, in the county of Polk and State of Iowa, haveinvented certain new and useful Improvements in Meansfor ProtectingContents of Oil-Containing Tanks Against Ignitionby ElectricalDischarge,of which the following is a specification.

0 One of the objects of my invention is to protect the contents ofstorage tanks, powder magazines, and other like Vreceptacles lfromdestruction by electrical discharge.

I accomplishk the object sought by surrounding the receptacle vwith acomplete 1nvclosing envelop, or housing, of electrically conductingmaterial and by extending the housing, or covering, below the surface ofl the ground upon which `thereceptacle is located, and I furthermoreelectrically connect the receptacle, at suitable intervals, tof-theoutside protecting envelop;

In carrying my invention into effect 4IV 'place the envelop sufficientlyfar removed from the receptacle to be without the danger zone ofignition of the inflammable gases, or other explosive media, thatemanate fro-m and which usually surround such receptacles.

In the accompanying drawing Figure l is a plan'view of an oil storagetank showing `it surrounded with my protecting envelop, or cage.. Fig. 2is a central vertical section of same. Fig. 3 is an enlarged detailedview ofV one of the vertically projecting rods or points adapted todisperse the direct lightning charge. Fig. 4 is an enlarged sectionalview of the portion ofy the tank, as shown broken away atthe lower righthand 4o corner of Fig. 2. 1 Vf In all the views the same referencecharacters are employed to indicate' similar parts.

In industrial oil fields, large numbers of tanks are usually connectedtogether by oil conducting pipes, and the tanks of each group aresimilarly connected to tanks of a like group and these groups may belocated at remote points, with respect to each other. The intermediateconducting pipes yare usuallyY placed underground, and in theirramifications they are distributed throughout large territories. Theytherefore afford large and extended surfaces, as conducting mediums,over which electrical oscillatory impulses may be propagated. The suddenand rapid rise and fall ofpotential, which is the physical manifestationof electrical oscillation, primarily due to an abrupt discharge withinthe inductive field of the conductor over which the oscillatory impulsespass, may inductively affect other electrical conductors within thefield of the conductor upon which they are impressed and frequentlyabrupt discharges, characterized as sparks which are of much smallersignificance than the primary discharge, are thus induced by theconductor of the first order in a neighboring conductor of the secondorder.

When a tank-containing inflammable v oil,-or any isolated body lofelectrical conducting material, within 'ignition distance, isinductively aiected by the supercharged pipes, atmosphere or ground, aspark may,

and in the natural order of things will beproduced between the chargedand uncharged bodies. The spark thus produced maybe ever so small, butwhen it occurs in the midst of a volume of explosive gases, ex-

perience has demonstrated that it will be of sufficient importance toignite the gases and destroy the contents of the receptacle .from whichthe gases may emanate. v -Electrical oscillations, originating fromtank, lor other receptacle, surrounded by my protecting means, with-theprotecting means itself, the igniting flame, brush, or spark, will notbe made upon the receptacle but will occur upon the outside surface ofthe inclosing envelop, or cage, which is fully beyond the danger zonesurrounding such receptacle.

In carrying my` invention into effect with a storage tank of 100 feet indiameter I preferably leave an annular space of about ten feet beta/eenthe outside surface ofthe tank and the vertical walls of the cage,within which space operators may freely pass around the tank. rlhisremoves the protecting device a sufficient distance from the outsideedges of the tank or away from the danger Zone immediately surrounding*the tank, as the gases coming from the tank at this distance away willbe sufficiently diluted as to be non-explosive.

In the illustrative embodiment 10 is the tank, 11 is the top, 12 and 13are. the conducting pipes for conducting oil or other inflammablematerial to and from the storage tank.

I n constructing my protecting cage I first dig a trench about two orthree feet deep around the tank and preferably, generally circular inform. and removed from the vertical walls of the storage tank about tenfeet, or I make the cage of a diameter about twenty feet greater thanthat of the tank, and in the trench I bury a tube or pipe, lll,preferably gas pipe, and having at suiiiciently frequent intervals Tsl5, into which to screw vertically disposed rods or pipes 16. I connecteach of the pipes 16, to the sides of the tank, as by means of anelectrical conductor pipe 17. Near the top of the tank I prefer toplace, between the respective vertically disposed rods, or tubes 16,horizontal tubes 18, similar-in character to those buried in the groundto form a second ring around the tank. In the top of each of the tubes16 I place a point 19, similar to points carried by lightning rods, forprotection of the tank from any abrupt discharge that may otherwise comedirectly from the clouds. To the ring 18, and the vertical rods or tubes16, I fix wire cloth fabric 20, and at proper points, in the verticalvwalls of the cage, I place doors 21, having fabric or other metalliccovering, through which doors employees may enter for access to thetank. Across the top of the structure I place a wire cloth cover 22supported on wire cables 23 that'are connected, as shown in Fig. 1,across the structure to the various vertically disposed posts 16 at thepoints where the ring 18 and the posts join.

Below the surface of the ground I place a wire fabric 22, somewhatheavier than the fabric Q2, as it is subjected to more rapiddeterioration from the acids, and electrolytic effects of the earth. A

I connect the pipes l2 and 13 to the cage, as at 12 and 13 respectivelyso that the cage will be of thesame electrical potential as the pipes.

An imperforate cage of sheet metal may be used instead of the metalfabric, with substantially equally good results. I prefer the reticulatecovering, however, as it inter-poses less wind resistance and istherefore more stable and enduring.

W'hile I have herein shown a single embodiment of my invention for t-hepurpose of clear disclosure, it is evident that changes may be madewithin the spirit of the invention within the scope of the appendedclaims.

Having described my invention, what I Y claim is 1. A cage forprotecting the contents of storage receptacles from ignition byelectrical disturbances comprising a circumferentially continuouselectrically conducting structure extending above and below thereceptacle and spaced apart therefrom; electric conductors connectingsaid structure and receptacle at intervals, and an electricallyconducting cover overlying said receptacle, electrically connected tosaid circumferential structure.

2. A cage for protecting the contents of storage receptacles fromignition by elec-| trical disturbances comprising two electricallycontinuous parallel rings, one above and the other below saidreceptacle; a series of vertically disposed rods included between therings at intervals and extending above the upper ring; walls, ofelectrically conducting material, extending between said rings,encompassing said receptacle and over the top thereof and electricalconduc tors connecting said receptacle with said protecting means. Y

In testimony whereof I hereunto set my hand in the presence of twowitnesses.

IVEST DODD. In the presence of- E. R. Mo'r'rs, T. I'V. DoDD.

Copies of this patent may be obtained for ve cents each, by addressingthe Commissioner of Patents. Washington, D. C.

